Section 7 - Relational databases and SQL

Question 1

What is the concept of a database and relational database?

Answer 1

Database:

• – Collecting information that is organised so it is easily accessible, manageable and updatable.
• – A database with one table is called a flat-file database

Relational database:
— Multiple tables linked together through their key fields

Question 2

What are the following database concepts:
• record
• field
• primary key
• foreign key

Answer 2

• – Records: all the data about one entity shown as rows
• – Fields: a single piece of data shown as columns
• – Primary key: a unique field/identifier for every record
• – Foreign key: a field in a table that is a primary key in another table

Question 3

Why are relational databases better than flat-file databases?

Answer 3

— Flat file databases have problems of inconsistency and redundancy therefore these issues are solved using relational databases.

• – Inconsistency is data being stored differently in the same table
• – Redundancy is data being stored more than once

Question 4

How do you retrieve data from tables in databases?

Answer 4

SELECT field(s)
FROM table(s)
WHERE condition
ORDER BY field ASC/DESC

Question 5

How do you insert data into a table?

Answer 5

INSERT INTO table(fields)

VALUES (values)

Question 6

How do you delete data in a database?

Answer 6

DELETE FROM table

WHERE field = value

Question 7

How do you edit data in a database using UPDATE?

Answer 7

UPDATE table
SET field = value
WHERE condition